#!/usr/bin/env node
const Koa = require('koa')
const send = require('koa-send')
const path = require('path')
const { Readable } = require('stream')
const compilerSFC = require('@vue/compiler-sfc')

const app = new Koa()

const streamToString = stream => new Promise((resolve, reject) => {
    const chunks = []
    stream.on('data', chunk => chunks.push(chunk))
    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf-8')))
    stream.on('error', reject)
  })

const stringToStream = text => {
    const stream = new Readable()
    stream.push(text)
    stream.push(null)
    return stream
}
  

// 3. 加载第三方模块
app.use(async (ctx, next) => {
    // ctx.path --> /@modules/vue
    if (ctx.path.startsWith('/@modules/')) {
      const moduleName = ctx.path.substr(10)
      const pkgPath = path.join(process.cwd(), 'node_modules', moduleName, 'package.json')
      const pkg = require(pkgPath)
      ctx.path = path.join('/node_modules', moduleName, pkg.module)
    }
    await next()
  })

//1、静态文件服务器

app.use(async (ctx,next)=>{
    //返回静态页面
    await send(ctx,ctx.path,{root: process.cwd(),index:"index.html"})
    await next()
})


// 4. 处理单文件组件
app.use(async (ctx, next) => {
    if (ctx.path.endsWith('.vue')) {
      const contents = await streamToString(ctx.body)
      const { descriptor } = compilerSFC.parse(contents)
      let code
      if (!ctx.query.type) {
        code = descriptor.script.content
        code = code.replace(/export\s+default\s+/g, 'const __script = ')
        code += `
        import { render as __render } from "${ctx.path}?type=template"
        __script.render = __render
        export default __script
        `
      } else if (ctx.query.type === 'template') {
        const templateRender = compilerSFC.compileTemplate({ source: descriptor.template.content })
        code = templateRender.code
      }
      ctx.type = 'application/javascript'
      ctx.body = stringToStream(code)
    }
    await next()
  })

// 2. 修改第三方模块的路径
app.use(async (ctx, next) => {

    if (ctx.type === 'application/javascript') {
      const contents = await streamToString(ctx.body)
      // import vue from 'vue'
      // import App from './App.vue'
      ctx.body = contents
        .replace(/(from\s+['"])(?![\.\/])/g, '$1/@modules/')
        .replace(/process\.env\.NODE_ENV/g, '"development"')
    }
  })

app.listen(3000)
console.log('server running @ http://localhost:3000')